1. Field of the Invention
This invention generally relates to a method for forming an electronic assembly, and more particularly, to a method for forming the printed circuit board.
2. Description of the Related Art
Printed circuited boards are widely used in electric equipment, such as cell phones, personal digital assistants, and thin film transistor liquid crystal devices. With development of technologies, the solder mask insulating layer of the printed circuit boards is required to have better uniformity to increase the yields of a solder paste printing process and micro solder ball printing process.
FIGS. 1A and 1B show three dimensional views of intermediate stages of a method for forming the printed circuit board of the conventional art. Referring to FIG. 1A, a substrate 102 is provided, wherein the substrate comprises a first device region 104, a second device region 106, and a dicing channel region 110 between the first device region 104 and the second device region 106. An insulating layer 105 is formed on the substrate 102. A circuit structure 108 is formed on the insulating layer 105, wherein the dicing channel region 110 between the first device region 104 and the second device region 106 does not comprise the circuit structure 108 for a subsequent dicing step to separate device units. Thereafter, referring to FIG. 1B, a solder mask layer 112 is coated on the circuit structure 108 and the insulating layer in the dicing channel region 110. However, as shown in FIG. 1B, since the top of the circuit structure 108 and the top of the insulating layer 105 in the dicing channel region 110 have a height difference. The coated solder mask layer 112 does not have a uniform thickness at the region neighboring the dicing channel region 110. Specifically, more serious sinking issues are generated for the solder mask layer 112 neighboring a cross of two dicing channel regions.
Therefore, a method for forming the printed circuit board which can eliminate the issue described previously is required.